Field of the Disclosure
The present disclosure generally relates to image processing and, more particularly, to an image processing device, an image processing method, a storage medium, and an image processing technique in which an image is formed by layering a color material layer and a gloss printing layer on a printing medium.
Description of the Related Art
In general, reproduction of an image on a printing medium by using an ink jet printer or the like involves halftone (HT) processing that determines dot arrangement of ink provided in the printer. When such HT processing is performed, it is necessary to prevent an unexpected regular pattern (artifact) such as moire from appearing. Japanese Patent Laid-Open No. 2001-157056 discloses the feature of HT processing that uses an error diffusion method, wherein an error is diffused in an outline direction detected in an image.
Meanwhile, printers, each of which reproduces gloss as well as color on a printing medium by providing a gloss ink such as a clear ink and a silver ink, are coming into widespread use. These printers each reproduce the color and the gloss by layering a color material layer formed by a color ink and a gloss printing layer formed by a gloss ink on a printing medium. When the gloss printing layer has a gloss that differs on an area basis while the color material layer has a color that differs on an area basis, in order to reproduce the color and the gloss with high accuracy, when each layer is formed, it is necessary to adjust an ink-dot discharge position on the basis of a position of an ink dot to be discharged to the other layer. However, in Japanese Patent Laid-Open No. 2001-157056, a position at which an ink dot is discharged is determined by referring only to a color image. Therefore, when the color material layer and the gloss printing layer are formed according to Japanese Patent Laid-Open No. 2001-157056, there arises a problem that a color-ink dot and a gloss-ink dot do not overlap with each other in an intended combination, and therefore the color and the gloss cannot be reproduced with high accuracy.